TwitterAuthenticator.AuthenticateUser backport attempt

twitterauthenticator.cs

    public static async Task<WebAuthenticationResult> AuthenticateUser(string twitterClientID, string twitterCallbackUrl
    {
        if (string.IsNullOrWhiteSpace(twitterClientID)) 
            throw new ArgumentException("TwitterClientID must be specified", twitterClientID);
        if (string.IsNullOrWhiteSpace(twitterCallbackUrl)) 
            throw new ArgumentException("TwitterCallbackUrl must be specified", twitterCallbackUrl);
        if (string.IsNullOrWhiteSpace(twitterClientSecret)) 
            throw new ArgumentException("TwitterClientSecret must be specified", twitterClientSecret);            
            
        var sinceEpoch = (DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0, 0).ToLocalTime());
        var rand = new Random();
        var twitterUrl = "https://api.twitter.com/oauth/request_token";
        var nonce = rand.Next(1000000000);
        var sigBaseStringParams = "oauth_callback=" + Uri.EscapeUriString(twitterCallbackUrl)
            + "&" + "oauth_consumer_key=" + twitterClientID
            + "&" + "oauth_nonce=" + nonce.ToString()
            + "&" + "oauth_signature_method=HMAC-SHA1"
            + "&" + "oauth_timestamp=" + Math.Round(sinceEpoch.TotalSeconds)
            + "&" + "oauth_version=1.0";
            
        var sigBaseString = "POST&" + Uri.EscapeUriString(twitterUrl) + "&" + Uri.EscapeUriString(sigBaseStringParams);

        var enc = new System.Text.UTF8Encoding();
            
        var keyMaterial = enc.GetBytes(twitterClientSecret + "&");              // CryptographicBuffer.ConvertStringToBinary(twitterClientSecret + "&", BinaryStringEncoding.Utf8);

        var hmacSha1Provider = System.Security.Cryptography.HMACSHA1.Create();  // var hmacSha1Provider = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1");
        hmacSha1Provider.Key = keyMaterial;                                     // var macKey = hmacSha1Provider.CreateKey(keyMaterial);
        var dataToBeSigned =  enc.GetBytes(sigBaseString);                      // CryptographicBuffer.ConvertStringToBinary(sigBaseString, BinaryStringEncoding.Utf8);            
            
            
        var signatureBuffer = CryptographicEngine.Sign(macKey, dataToBeSigned);            
            
            
        var signature = Convert.ToBase64String(signatureBuffer);                // CryptographicBuffer.EncodeToBase64String(signatureBuffer);            
        var dataToPost = "OAuth oauth_callback=\"" + Uri.EscapeUriString(twitterCallbackUrl) 
            + "\", oauth_consumer_key=\"" + twitterClientID 
            + "\", oauth_nonce=\"" + nonce.ToString() 
            + "\", oauth_signature_method=\"HMAC-SHA1\", oauth_timestamp=\"" + Math.Round(sinceEpoch.TotalSeconds) 
            + "\", oauth_version=\"1.0\", oauth_signature=\"" + Uri.EscapeUriString(signature) + "\"";
            
        var response = await PostData(twitterUrl, dataToPost);
            
        if (string.IsNullOrWhiteSpace(response))
        {
            return null;
        }
            
        String oauth_token = null;
        String oauth_token_secret = null;            
        var keyValPairs = response.Split('&');            
        for (int i = 0; i < keyValPairs.Length; i++)            
        {                
            var splits = keyValPairs[i].Split('=');                
            switch (splits[0])                
            {                    
                case "oauth_token":
                    oauth_token = splits[1]; 
                    break;
                case "oauth_token_secret":
                    oauth_token_secret = splits[1];         
                    break;        
            }       
        }          
        if (string.IsNullOrWhiteSpace(oauth_token))       
            return null;               
        twitterUrl = "https://api.twitter.com/oauth/authorize?oauth_token=" + oauth_token;    
        var startUri = new Uri(twitterUrl);    
        var endUri = new Uri(twitterCallbackUrl);   
        return await WebAuthenticationBroker.AuthenticateAsync(WebAuthenticationOptions.None, startUri, endUri);
    }